Sealed rotary actuator



March 6, 1962 B. E. O'CONNOR SEALED ROTARY ACTUATOR Filed April 29, 1960 mm? w m k; 2 Va #7 md r p 4 B 4 N. 5M Y B United States Patent 3,023,741 SEALED ROTARY ACTUATGR Bernard E. OConnor, Playa Del Rey, Caiifi, assignor to Clemco Aero Products, a corporation of New York Filed Apr. 29, 196i), Scr. No. 25,778 3 Claims. (Cl. 121-99) This invention relates to hydraulic actuator mechanisms, and more particularly to an improved sealed rotary actuator suitable for operation with pivo-tally adjustable devices in aircraft, such as elevators, ailerons, wingflaps, and the like.

A rotary actuator is the desired form of actuator for operation with a pivotally mounted device. In this connection, the shaft of a rotary actuator is located on the same axis as the pivotal mounting for the device. Thus, a given angular movement of the actuator shaft is directly converted into the same angular movement for the device that is pivotally mounted therewith. Therefore, the rotary actuator constitutes an extremely compact device for impartins angular movement to a pivotally mounted element. Such compactness cannot be attributed to linear actuators, wherein longitudinally slidable pistons necessarily require a considerable amount of space.

One of the strongest arguments heretofore advanced against the acceptance of rotary actuators for the abovementioned purposes is the difliculty in suitably sealing such actuators against leakage of fluid between the working chambers thereof. Such chambers are formed by providing the actuator shaft with elongated radial shoulders or ribs that extend into spaces between circumferentially spaced, inwardly projecting ribs of the surrounding housing. The outer surface of a rib on the shaft is in sliding en agement with the inner wall of the housing, and the inner surface of a rib of the housing is in sliding engagement with the lateral surface of the shaft. Thus, there is an elongated chamber on both sides of the radial surfaces of each rib.

The direction of movement of the shaft relative to its housing is determined by the difference in fluid pressure on the opposite sides of a rib of the shaft. It is of utmost importance that there be no leakage of fluid from the high-pressure chamber to the low-pressure chamber. One way to minimize leakage is to make all abutting surfaces carefully machined, highly polished surfaces. However, such precautions still result in an undesirable quantity of fluid leakage between chambers. Such minimum leakage is too much to be permitted in many hydraulic actuators.

t is an object of this invention to provide an improved rotary actuator that eliminates the above and other disadvantages of prior-art rotary actuators.

It is another object of tins invention to provide an improved rotary actuator which efiectively minimizes leakage of hydraulic fluids between chambers containing fluids at different pressures.

A further object of this invention is to provide an improved rotary actuator construction, in which sealing elements are cooperatively arranged to substantially prevent the leakage of fluid from a high-pressure chamber to a low-pressure chamber around any part of the shaft or its housing.

Yet another object of this invention is to provide an improved rotary actuator having a minimum number of component parts of simple design and rugged construction.

The above and other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawing of an illustrative embodiment thereof, in which:

FIGURE 1 is a longitudinal sectional view of a rotary 3,023,741 Patented Mar. 6, 1962 actuator in accordance with my invention, showing the shaft grooved at the ends of the ribs thereon, and expansible seals disposed in such grooves and abutted by the ends of respective spring elements that extend lengthwise of the ribs;

FIGURE 2 is a sectional view taken along the line 2-2 of FIGURE 1, showing the relative positions of the actuator parts intermediate the ends of the shaft;

FIGURE 3 is an enlarged, fragmentary perspective view of the shaft of the actuator of FIGURE 1, showing the overlying portion of the housing in phantom, to aid in explaining the leakage paths that have heretofore existed in rotary actuators, and which are avoided in the actuator construction of my invention; and

FIGURE 4 is a fragmentary perspective view of the ends of the expansible sealing elements used in my improved actuator.

Referring to FIGURE 1, there is shown a housing 10 in which a shaft 11 is rotatably mounted, for connection to respective elements (not shown) wherein one rotates relative to the other. Such connections may be made by suitably keying the shaft 11 to the shaft on which one device is mounted, and by securing the housing 10, as by a flange 12 thereon, to the other device.

Referring to FIGURE 2 along with FIGURE 1, the housing 10 is provided internally with a central bore 13, from which a number of circumferentially spaced ribs 14, 15, 16, and 17 extend. As shown, the ribs 14, 16 and 15, 17 are diametrically opposed. The distance between the diametrically opposed ribs is the diameter of the shaft 11.

Within the housing 16, and coextensive with the ribs 14-17 thereof, the shaft 11 is provided with circumferentially spaced ribs 21, 22, 23, and 24. The radial dimensions of the ribs 21-24 and the ribs 14-17 are the same, whereby to permit the inner surfaces of the ribs 14-17 of the housing to engage the lateral surface of the shaft 11, and the outer surfaces of the ribs 21-24 to engage the wall of the bore 13.

With the shaft 11 located in the housing 19 so that the ribs 21-24 thereof are coextensive with the ribs 14-17 of the housing, a pair of nut elements 25, 26 are placed over the shaft 11 and threadedly secured in the housing. As shown in FIGURE 1, the ends of the ribs 21-24 are in abutment with the elements 25, 26. With this arrangement, it will be seen that the ribs 21-24 (together with the adjacent pairs of ribs 17-14, 14-15, 15-15, and 16-17, and the end elements 25, 26 define pairs of chambers 27-28, 29-30, 31-32, and 33-34. From these pairs of chambers, respective chambers 28, 30, 32, and 34 are in fluid communication with each other. Similarly, the remaining chambers 27, 29, 31, and 33 are in fluid communication with each other.

As shown, the chambers 27 and 28 are connected rough respective port connections 37, 38 to the exterior of the housing 10, such port connections 37, 38 being adapted for connection to a hydraulic-fluid source (not shown). As will be apparent, the positions of the ribs 21-24, and hence the angular position of the shaft 11, is dependent upon the difference between the fluid pressures in the chambers on the opposite sides of such ribs.

To insure that no hydraulic fluid will escape from the housing 10 in the axial direction, conventional O-ring seals 49, 41 are provided around the shaft 11 and suitable grooves formed in the end elements 25, 26, and by O-rings 42, 43 surrounding the end elements 25, 26. The O-rings 46-43 represent conventional means for preventing leakage of fluid between two concentric surfaces.

With the axial leakage avoided, this leaves the problems of leakage of fluid between the high-pressure chambers and the low-pressure chambers. The possible paths for such leakage between chambers are around the outer surfaces of the ribs 21-24, around the inner surfaces of the ribs 14-17, and around the ends of these ribs. This is shown more clearly in FIGURE 3 wherein arrows 45, 46 illustrate leakage paths around the ends of the ribs 17, 21, and arrows 47, 48 illustrate the leakage paths, respectively, between the inner surface of the rib 17, and the shaft 11, and between the outer surface of the rib 21 and the housing 10.

To avoid the possibility of leakage of fluid along the paths 47, 48, I utilize a slotted construction for the ribs 14-17 and 21-24, the ribs being slotted longitudinally as indicated more clearly in FIGURE 3, and I employ elongated strips of packing material in the slots that are spring-biased to abut the confronting surface with which the rib is in abutment. Referring to FIGURE 1, such sealing for the ribs 21-24 on the shaft 11 is effected by elements 51, 52 of packing material in the shape of an elongated U to conform to the slot formed in the ribs 21-24. At the bottom of the slots in the ribs 21-24, there are provided respective spring elements 53. As shown, the springs 53 are elongated, ribbon-like elements, the vertical legs of which terminate in horizontal end portions against which the ends of the legs of the packing elements 51, 52 are located. The packing elements 51, 52, which are placed side by side in the slots in each of the ribs 21-24, are each split along their lengths so that the two parts thereof can be separated longitudinally. However, the splits 51' in the elements 51 are longitudinally spaced from the split portions 52' in the elements 52. As will be seen, such arrangement of the split portions of these packing elements avoids the formation of a leakage path through the bodies of these elements.

When the springs 53 and the packing elements 51, 52 are initially assembled in the ribs 21-24 as illustrated, the springs 53 are normally flexed so as to bow outwardly along their lengths. Then, when the shaft 11 is inserted in the housing, so that the ribs 21-24 are located intermediate the ribs 14-17 on the housing, the packing elements 51, 52 and the springs 53 are forced inwardly along their lengths. In this manner, the packing elements 51, 52 are biased outwardly by the springs 53 into engagement with the inner wall of the bore 13, such bias being suflicient to insure constant engagement of the packing elements 51, 52 with the inner wall of the bore, so as to prevent the possibility of hydraulic fluid leaking around the ribs 21-24 past the packing elements, i.e., along the paths 48.

As indicated in FIGURES 2 and '3, the ribs 14-17 of the housing are slotted in the same manner as the ribs 21-24, and similar springs 55 and packing elements 56, 57 are located in the ribs 14-17, the arrangement of the slots and the elements 55-57 being reverse to the arrangement in the ribs 21-24, so that the springs 55 bias the packing elements 56, 57 inwardly into engagement with the lateral surface of the shaft 11. In this manner, it will be seen that my actuator is effectively sealed against leakage along the paths 47, 48 indicated in FIGURE 3.

To avoid the possibility of leakage along the paths 45, 46 indicated in FIGURE 3, i.e., around the ends of the ribs 14-17 and 21-24, I provide circumferential grooves 60 in the surface of the shaft 11 immediately adjacent the ends of the ribs 21-24. Also, I provide short axial slots 61 in the shaft 11 at the centers of the ribs 21-24, such slots 61 being coextensive with the ends of the legs of the slots in the ribs 21-24. As shown, the axially extending ends of the legs of the springs 53 (see FIGURE 1) are located in the main body of the shaft in such axial slot portions, and extend to the extreme ends of the ribs 21-24.

Within the grooves 60 in the shaft 11, I locate expansible ring elements 63, which tend to expand radially and thereby provide a tight seal against the inner surfaces of the end elements 25, 26 and immediately adjacent the extreme ends of the ribs 14-17 and 21-24. The rings are pressure loaded against the sides of the grooves 60 nearest the ends of the ribs, as by means of check valves indicated diagrammatically at 67 from the inlets 37. Such pressure loading of the rings, together with the outward bias of the expansible seal elements 63 and the axial thrust by the springs 53 against the seals 51, 52, prevents hydraulic fluids from leaking around the ends of the ribs 14-17 and 21-24, Thus, my improved actuator provides effective sealing against leakage around the radial and circumferential surfaces of the ribs. This sealing is so effective as to permit the shaft to be supported for rotation in low friction bearings 69 located in the end elements.

One form of construction of expansible-ring seal element 63 is shown in FIGURE 4. The element 63 is a split ring element, wherein one end is notched and shaped to form a finger element 64, and the other end is notched, as at 65, to slidably receive the finger 64. In the uncompressed condition of the ring 63, the finger 64 is substantially removed, circumferentially, from the notched portion 65 in the opposite end of the ring. In assembling such a ring on the shaft 11, the ring is compressed circumferentially to force the finger 64 into the notch 65. Since the ring in the compressed condition is of the proper size to fit within the circumferential grooves 60 in the shaft 11, the spring characteristics of the ring cause it to tend to expand radially. This expansion characteristic causes the lateral surface portions of the ring to be firmly biased against the inner surfaces of the end elements 25, 26.

While I have illustrated and described a particular embodiment of my invention, it will be apparent that various modifications may be made without departing from the spirit and scope of my invention. For example, double rings, like the ring 63, may be employed; also solid rings (e.g. metal, Teflon, etc.) may be used as by relatively expanding the ring and shrinking the shaft in order to assemble the ring in the groove. Accordingly, I do not intend that my invention be limited, except as by the appended claims.

I claim:

1. In a rotary actuator, the combination of: a shaft having spaced radial ribs; a housing surrounding said shaft having spaced inwardly projecting shoulders, a shoulder being located intermediate adjacent ribs, said shoulders being of the same radial dimension as said ribs, said shoulders and ribs being coextensive; sealing means for said ribs and said shoulders to prevent leakage of fluid along the circumferential surfaces of said ribs and shoulders; sealing means at the ends of the ribs and shoulders to prevent leakage of fluid around the ends of said ribs and shoulders, including ring elements surrounding said shaft at the ends of said ribs; and means for applying fluid under pressure to the outer radial surfaces of said ring elements and force them into sealing engagement with said ribs.

2. A rotary actuator comprising: a shaft having spaced radial ribs, said shaft having circumferential grooves at the ends of said ribs; a housing surrounding said shaft having spaced inwardly projecting shoulders, a shoulder being located intermediate adjacent ribs, said shoulders being of the same radial dimension as said ribs, said shoulders and ribs being coextensive; expansible ring seal elements in said grooves to prevent leakage of fluid along the end surfaces of said ribs and shoulders; and means to permit fluid under pressure to be applied against the outer radial surfaces of said ring seal elements, thereby causing the inner radial surfaces of said ring seal elements to sealingly abut the ends of said ribs.

3. A rotary actuator comprising: a shaft having spaced radial ribs, said ribs being slotted along their lengths, said shaft having a circumferential groove therein at each end of said ribs; a housing surrounding said shaft having spaced inwardly projecting shoulders, a shoulder being located intermediate adjacent ribs, said shoulders being of the same radial dimension as said ribs, said shoulders and ribs being coextensive, said shoulders being slotted along their lengths, said housing being threaded adjacent the ends of said shoulders; nut elements threaded into said housing and abutting said shoulders and ribs; sealing elements in the slots; means biasing said sealing elements radially; expansible ring seal elements in said grooves to prevent leakage of fluid along the end surfaces of said ribs and shoulders, the width of each ring seal element being less than the width of the groove in which it is located; and means to pressure-load said ring seal elements inwardly, including fluid connections through said nut elements to the outer portions of said grooves, whereby fluid under pressure acts through said connections to force said ring seal elements axially into sealing engagement with the inner faces of the grooves and the adjacent sewing elements.

References Cited in the file of this patent UNITED STATES PATENTS 

